Achieve C90 compliance and test in CI

[mkannwischer]

• Depends on CI: Perform ACVP tests #4
• Resolves CI: Test C90 compliance in CI #11

[mkannwischer]

First step would be to replace inline by SLH_INLINE and create a sys.h (or similar) that defines it.

In mlkem-native we are using

/*
 * C90 does not have the inline compiler directive yet.
 * We don't use it in C90 builds.
 * However, in that case the compiler warns about some inline functions in
 * header files not being used in every compilation unit that includes that
 * header. To work around it we silence that warning in that case using
 * __attribute__((unused)).
 */

/* Do not use inline for C90 builds*/
#if !defined(MLK_INLINE)
#if !defined(inline)
#if defined(_MSC_VER)
#define MLK_INLINE __inline
/* Don't combine __inline and __forceinline */
#define MLK_ALWAYS_INLINE __forceinline
#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
#define MLK_INLINE inline
#define MLK_ALWAYS_INLINE MLK_INLINE __attribute__((always_inline))
#else
#define MLK_INLINE __attribute__((unused))
#define MLK_ALWAYS_INLINE MLK_INLINE
#endif

#else /* !inline */
#define MLK_INLINE inline
#define MLK_ALWAYS_INLINE MLK_INLINE __attribute__((always_inline))
#endif /* inline */
#endif /* !MLK_INLINE */

[mkannwischer]

We need to work on the speed of these tests. I want to avoid requiring parallel for basic testing. basic tests should work without installing dependencies.

[mjosaarinen]

all looks good.